Compositions to reduce friction are well known, including those suitable for use as release agents. Many friction reducing compositions are based on mineral oils which, although often effective, are now becoming generally undesirable due to environmental and health concerns.
Accordingly there is a need for environmentally friendly friction reducing compositions in many technical fields.
One area where a mineral oil, usually in the form of diesel, has been extensively used is in the manipulation and transport of asphalt. The majority of roads, car parks and the like are constructed using asphalt, which is a combination of aggregate and bituminous components. Asphalt is generally manufactured at a plant and then transported to an area of construction on a vehicle, often a “dump truck” or similar vehicle having a bed for holding the asphalt. It is then applied as required for the particular task, e.g. using road laying equipment. Asphalt is inherently adhesive and tends to stick to any surface it contacts, i.e. the bed of the transport truck, and tools or apparatus used in laying or maintaining the asphalt. Traditionally this has been combated by coating surfaces which are to be in contact with the asphalt with diesel which acts as a lubricant between the asphalt and the surface. One disadvantage of diesel in this role is that is can partially dissolve and “soften” the asphalt; this may be advantageous in allowing it to slide relatively easily from the surface, but it can degrade the quality of the resultant asphalt. Use of diesel in such a role has, however, become unacceptable for environmental and health reasons. Accordingly, there is a need for alternative compositions and methods for preventing undesirable adhesion of asphalt to surfaces. Such compositions should be environmentally friendly, effective and cheap enough to be economically viable.
U.S. Pat. No. 6,486,259 describes a combination of a polyvinyl alcohol, glycerol, polyethyleneglycol and a wetting agent or surfactant which are suitable for use as an asphalt release agent. U.S. Pat. No. 5,494,502 discloses an asphalt release agent which comprises a fatty oil as the active ingredient in combination with a surfactant or foaming agent.
Another area where release agents are required is for the release of objects from mould in which they were formed. For example, a particularly significant field is in the release of pre-formed concrete or other hydraulic bonding materials (e.g. cement or plaster) from moulds. This has been achieved in the past using mineral oil, often with additives such as retarding agents to prevent curing of the concrete at its surface, as well as wetting agents or corrosion inhibitors. Such agents can, in some instances, have disadvantages in that they may adversely affect the surface of the concrete. Other areas where mould release agents are required are, for example, rubber or plastics moulding, foundry moulding, and clay or terracotta moulding. As with asphalt release, the use of mineral oils in these areas is highly undesirable from an environmental and a health perspective. Accordingly, there is a requirement for non-toxic, environmentally friendly release agents in these fields.
U.S. Pat. No. 5,374,303 describes a release agent for hydraulic bonding materials which comprises an oil component, which is an ester of a hindered polyhydric alcohol and a straight or branched chain saturated or unsaturated C4-C24 monocarboxylic acid. A surfactant is used to create an aqueous emulsion of the oil component. U.S. Pat. No. 5,709,739 describes a release agent for hydraulic binders which comprises water, an oil component comprising a water-immiscible monohydric alcohol and an emulsifier. U.S. Pat. No. 5,474,604 describes a composition suitable for use as a release agent in, e.g. the building, rubber and plastics processing industries. The composition comprises fatty alcohols having 16 to 24 carbon atoms, wax esters and fatty ketones. U.S. Pat. No. 5,100,697 describes a release agent which comprises an oil and water emulsion comprising an oil component bath and an ionic and a non-ionic surfactant.
In the general field of release agents, in particular the more specific fields of asphalt release agents and mould release agent, there is a general consensus that release agents used to replace mineral oils are usually both more expensive and less effective than their mineral oil counterparts. Accordingly, there is a need for improved friction reducing compounds which are both effective and economical.
Improved friction reducing compositions, particularly release agents, may have utility in other fields of industry, for example, in metal deformation, forging or machining.
Liquid crystals are well known in certain areas of technology, particularly thermotropic liquid crystals which are noted for their use in display technology. However, there is another form of liquid crystals known as lyotropic liquid crystals which are less well known. Lyotropic crystals are formed from amphiphilic compounds (e.g. surfactants) which are characterised by consisting of molecules in which one end of the molecule is polar and the other end is non-polar. When dispersed in water, certain amphiphilic compounds take on a liquid crystal structure at particular concentrations. As the concentration of such surfactants increases the liquid crystal can, in many instances, change from a cubic liquid crystal to a hexagonal form and then a layered or lamellar phase—this is described in more detail below. Lyotropic liquid crystals, in general, rarely exist in solutions that are less that half amphiphile by weight and lamellar liquid crystals typically form at even higher concentrations.
Lamellar liquid crystals are known for use in the cosmetic industry, however, use outside this field is not generally recognised. WO 2005/102265 discloses a surfactant composition capable of forming liquid crystals in water which comprises at least one sorbitan ester and at least one sorbitol ester, wherein the mean number of carbon atoms in the hydrophobe of the sorbitan ester is greater than that of the sortitol ester. WO 2004/111168 discloses surfactant compositions comprising at least one branched non-ionic surfactant and at least one surfactant capable of forming liquid crystals in water. In both the two aforementioned patent applications the compositions disclosed are for use as cosmetic compositions.